You have a problem with the SD card, you can't reflash if the card doesn't work.
Examples in Mio gps in reflash mode.
Spoiler: Ex. video ROM in Mio
Mio C520:
[Only registered and activated users can see links. ]
Mio C220:
[Only registered and activated users can see links. ]
Medion GoPal:
[Only registered and activated users can see links. ]

Check the SD reader terminals.
It is very common to happen that some lash is twisted, it is common in GPS MIO:
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